[Strawbale] PEX tubing in floors

[David Neeley]

Shody,

> I see, so a deicing loop would only be needed on a
> evac tube collector because of its insulation and
> shape, flat plate (closed loop) will deice itself.

No, a deicing loop would likely *not* be necessary on an evacuated
tube system, as the vacuum is the ultimate insulation. The tubes will
not freeze. The manifold wherein the water is heated at the head of
the tube would normally be well insulated, though, since at night the
tube would not be making it hot and so avoid icing--although it could
also be done as a drain-down system with not enough moisture left
there to matter at night.

Furthermore, a flat plate collector *will* freeze, which is why many
people use antifreeze in them to avoid that problem by lowering the
freezing temperature of the working fluid below any temperature your
climate will present. Antifreeze is less efficient than plain water,
however, and then of course you have the heat exchanger which is also
less efficient--meaning you need more collector area for the same
effective heating than you would for a direct-gain
collector...although that is mostly a theoretical distinction.

> I gess the other problem with radiators filled with
> cold water to cool the air would be humidification of
> the cooled air? This is a little confusing; if the air
> temperture is lowered without dehumidification, would
> the air become more humid than leaving it the same
> temperature?

No. Cooling warmer air will release moisture quite often, since the
warmer the air is the more moisture it can carry--and, in any kind of
humidity, it *does* carry. Thus, when you cool it the moisture it can
no longer carry is dropped in the form of water or water vapor. The
air exiting the radiators would be less moist (other than any water
vapor carried physically along with it) than the warmer entry air,
with water being deposited on and around the radiators.

>If the relitive humidity increases, for
> the comfort of humans, should dehumidifcation also
> take place, hense the popularity of regular A/C
> because it does both?

In many places, summer air is both warm and humid. When it is humid,
less of your own perspiration can evaporate, leaving you uncomfortably
warm. (This is why desert heat does not seem so oppressive since it is
hot but dry).

This is why an air conditioner can be quite comfortable, too, as it
needn't be kept as cold since it also dehumidifies to a more
comfortable level. That allows your body to work as it was designed
to--cooling you through evaporation of the sweat we are constantly
releasing.

In winter, by contrast, the cold air outside carries less
humidity...and simply warming it will not cause it to gain humidity
unless there is a source for it. Thus, inside air is often too dry for
our comfort. This is why we may install a humidifier for winter
air--or put a pan of water on the heater or on the stove, as our
grandparents often did. Increasing the humidity somewhat in winter is
often helpful in helping you breathe better, and again you will feel
warmer at somewhat lower temperatures when the air contains a
respectable amount of humidity.

David